In optoelectronic linear, angular, or rotary position encoders, at least one coded track of a code carrier or encoder is typically illuminated, and a sensor measures the change in intensity of the light through the coded track in response to a movement of the code carrier. In a method using transmitted light, a light source is configured so that its light beam is transmitted through a transparent code carrier, whose light and dark sections are formed by regions with varying transparency. In a method using an incident-light, or vertical illumination principle, a coded track is illuminated, whose light and dark fields are formed by areas that reflect the light to a greater or lesser degree.
A very fine division of the coded track into light and dark graduation fields necessitates a slit aperture that is subdivided into transparent light-transmitting regions of varying transparency, in accordance with the light and dark fields of the coded track. This means that the maximum quantity of light is transmitted through only when the coded track and slit aperture are coincidently positioned. As a result, an optoelectronic sensor, which is positioned on the side of the assembly that is remote from the light source, receives a fully modulated light signal. Assigned to each coded track is a photosensor, which receives the transmitted light signal.
A separate photoelectronic component can be allocated to each coded track. This is also the case in opto-arrays, which combine a plurality of photosensors into one component. However, in this case, it is difficult to precisely align the aperture to the photoelectronic component with the code carrier.
An optoelectronic linear, angular, or rotary position encoder is proposed in EP 0 564 683 A1. An optoelectronic sensor is configured on the side of a plate-shaped aperture stop remote from the encoder. The sensor has contact points that face the plate-shaped aperture stop, and contact the electrical printed conductors on one side of the plate-shaped aperture stop. The aperture structure can be formed in a coating of the plate-shaped aperture stop.
This structure requires substantial effort and cost for manufacturing. The aperture structure can become damaged when mounting the semiconductor chip on the plate-shaped aperture stop. If an application requires a different aperture structure, it is necessary to fabricate a completely new plate-shaped aperture stop.
In addition to providing an aperture structure in front of light-sensitive sensor surfaces of optoelectronic sensors, certain optical scanning devices also use an aperture structure placed in front of the light source in question. In such a decision, it may be necessary to use emitter gratings, for example, like the ones in an arrangement described in German Patent DE 195 27 287. In a design using emitter gratings, the cost and inflexibility discussed above are also a factor when manufacturing the unit.
The embodiments of the present invention are directed to optoelectronic linear, angular, or rotary position encoders, particularly in view of simplifying the implementation of various aperture structures. The optoelectronic linear, angular, or rotary position encoder can have an illuminated or transilluminated code carrier, which can include at least one coded track having either alternating reflecting and non-reflecting zones, or transparent and opaque zones defining light and dark fields. Different configurations can thus be used to provide alternating light projecting zones and light non-projecting zones.
Artificial light, and even daylight, can be used as a light source. In addition, the device can include an aperture platelet, which is disposed in the path of the light modulated by the code carrier. The aperture platelet has an aperture structure with regions that are transparent to a greater or lesser extent, corresponding to the light and dark fields of the coded track, and which is joined to a transparent substrate that supports at least one optoelectronic sensor chip facing the aperture structure.
In one aspect, the invention is thus an opto-electronic linear, angular, or rotary position encoder is described. The device includes a light modulating code carrier comprising at least one coded track having adjacent light projecting and light non-projecting portions and an aperture structure disposed in a path of light being modulated by the code carrier. The device further includes a transparent substrate supporting at least one opto-electronic sensor chip facing the aperture structure, wherein the aperture structure is disposed on an aperture platelet, and the aperture platelet is joined to the substrate.
In one embodiment of the invention, the aperture structure is arranged only in front of the optoelectronic sensor chip. Alternative embodiments in accordance with the present invention can provide also for configuring an aperture structure formed by an emitter grating disposed in front of the light-emitting surface of a suitable light source.
The aperture platelet, which is preferably a glass wafer that can have a coating, scribe line or embossing forming the aperture structure, can be manufactured separately. Different applications thus only require producing different aperture platelets. On the other hand, the transparent substrate, together with the sensor chip mounted thereon, forms an assembled structure that can be produced without changes for a plurality of application cases. Thus, the aperture platelet and assembled structure can serve as a model for various applications, in the manner of a unit construction system.
The transparent substrate can be provided with printed conductors, to connect the chip at its contact points to the printed conductors using a xe2x80x9cflip-chip assemblyxe2x80x9d method. The transparent substrate can be glass, plastic, or another suitable material. In the first case, the chip assembly can also be referred to as xe2x80x9cchip-on-glass assemblyxe2x80x9d. In addition, the chip can be protected on the substrate by encapsulating material. The aperture platelet can preferably have at least one projection beyond the transparent substrate with edges defined with respect to the aperture structure, making it possible to precisely align the aperture structure.
The aperture platelet can be joined to the transparent substrate by bonding or by using other interconnect technologies. Also, an interconnect technology can be used which makes it possible to replace the aperture platelet in a later step.